What is a risk-limiting audit, and how do you perform one? An RLA is a human inspection of a random sample of the paper ballots (or batches of ballots)—using a scientific method that guarantees with high confidence that if the voting machines claimed the wrong winner, then the audit will declare, “I cannot confirm this election,” in which case a by-hand recount is appropriate. This is protection against voting-machine miscalibration, or against fraudulent hacks of the voting machines.

That’s what it is, but how do you do it? RLAs require not only a statistical design, but a practical plan for selecting hundreds of ballots from among millions of sheets of paper. It’s an administrative process as much as it is an algorithm.

In 2018, RLAs were performed by the state of Colorado. In addition, two just-published reports describe pilot RLAs performed by Orange County, California and Fairfax, Virginia. From these reports (and from the audits they describe) we can learn a lot about how RLAs work in practice.

Neal Kelley, Registrar of Voters of Orange County, ran an RLA of 3 county-wide races in the June 2018 primary, with assistance from Verified Voting. About 635,000 ballots were cast; many ballots were 3 pages long (printed both sides), about 1.4 million sheets overall. Of these, just 160 specific (randomly selected) ballot sheets needed to be found and tabulated by human inspection. How do you manage a million sheets of paper?

Orange County elections warehouse during the June 2018 risk-limiting audit

Like this! Keep well organized ballot manifests that list each batch of ballots (that were initially counted by optical scanners), where they came from, how many ballots. How do you know how many ballots are in each batch? The optical scanners tell you, but you don’t want to trust the optical scanners (a hacked scanner could influence the audit by lying about how many ballots are in a batch). So you weigh the batch on a high-precision scale, that tells you ±2 sheets. And so on. You can read the details in the report, which really helps to demystify the process. Still, there are many ways of doing an RLA, and this report describes just one of them. The audit was finished before the deadline for certifying election results. The estimated salary cost of the staff of the Registrar of Voters, for the days running the audit, was under $4000.

Brenda Cabrera, General Registrar of the City of Fairfax, ran a pilot RLA of the June 12th 2018 Republican primary Senate election, with assistance from Verified Voting. There were 948 ballots cast, and the audit team ran the audit three ways, to test three different RLA methods. The audit was scheduled to take two days but finished ahead of schedule.

Ballot-marking devices (BMD) contain computers too, and those can also be hacked to make them cheat. But the principle of voter verifiability is that when the BMD prints out a summary card of the voter’s choices, which the voter can hold in hand before depositing it for scanning and counting, then the voter has verified the printout that can later be recounted by human inspection.

ExpressVote ballot card, with bar codes for optical scanner and with human-readable summary of choices for use in voter verification and in recount or audit.

But really? As a practical matter, do voters verify their BMD-printed ballot cards, and are they even capable of it? Until now, there hasn’t been much scientific research on that question.

In a real polling place, half the voters don’t inspect their ballot cards, and the other half inspect for an average of 3.9 seconds (for a ballot with 18 contests!).

When asked, immediately after depositing their ballot, to review an unvoted copy of the ballot they just voted on, most won’t detect that the wrong contests are presented, or that some are missing.

This can be seen as a refutation of Ballot-Marking Devices as a concept. Since we cannot trust a BMD to accurately mark the ballot (because it may be hacked), and we cannot trust the voter to accurately review the paper ballot (or even to review it at all), what we can most trust is an optical-scan ballot marked by the voter, with a pen. Although optical-scan ballots aren’t perfect either, that’s the best option we have to ensure that the voter’s choices are accurately recorded on the paper that will be used in a recount or random audit. [Read more…]

In November 2018 I got opinions on voting machines and vote-by-mail from 17 experts on election verification, who have experience running/observing/studying elections in 17 states.

On the acceptability of these in-the-polling-place voting technologies, in the context of U.S. elections:

The consensus is that Direct Recording Electronic voting machines are unacceptable, even with a VVPAT (“voter verified paper audit trail visible to the voter under glass”). Most experts are lukewarm to hand-counted paper ballots, presumably because they’re impractical for large elections with many contests on the ballot. Most experts prefer hand-marked optical scan ballots, and all of these experts find hand-marked optical scan acceptable. Most experts are willing to accept ballot marking devices (BMDs) that prepare “bubble ballots” to be scanned by optical scan machines, but only 17% find this preferable to hand-marked optical-scan ballots. Opinion is mixed on BMDs that prepare bar-code ballots (with human-readable summaries) for tabulation by optical scanners, with most finding this technology at least “barely acceptable.” Almost no one prefers all-in-one machines that combine ballot marking and ballot scanning (but at least the voter can hold the ballot in her hand while inspecting it), with about a 50/50 split between “acceptable” and “barely acceptable”.

Most experts don’t prefer ballot-marking devices (BMDs) for these reasons:

If the paper jams, the power fails, or something else goes wrong with technology, voters using hand-marked paper ballots can still deposit their ballots in an emergency ballot for counting later; this is not an option with a BMD-only solution.

BMDs are more susceptible to fraud: if a BMD wrongly marks a paper ballot, (studies have shown that) most voters won’t notice.

BMDs cost $5000, pens cost 50c; it is expensive to supply enough BMDs for all voters, but it is feasible to supply BMDs sufficient for those voters unable to mark a paper ballot by hand.

A few experts (17%) prefer BMD-marked ballots to hand-marked ballots because (1) there’s no chance of ambiguous marks and (2) it’s easier to give voters feedback about undervotes/overvotes.

Regarding vote-by-mail: There is no consensus on whether vote-by-mail increases voter turnout. Almost all the experts agree that vote-by-mail seriously compromises the secret ballot, and that it still matters whether we have coercion-resistant secret balloting. Most experts are not confident that ballots are not interfered with between the time they leave the voters’ hands and the time they are counted, and are not confident the chain of custody for mail-in ballots could be made adequately secure. The experts agree that it is essential to have public observation of all the steps in handling mail-in ballots, but almost none of the experts believes that there is adequate public observation in their own jurisdictions.That is not to say that the experts are against vote-by-mail; it’s just that there are some issues that ought to be discussed and improved.

Freedom to Tinker is hosted by Princeton's Center for Information Technology Policy, a research center that studies digital technologies in public life. Here you'll find comment and analysis from the digital frontier, written by the Center's faculty, students, and friends.